The Fourth International Symposium on Innovative Nuclear Energy Systems, INES-4In the development of JENDL-4.0, the thermal and resonance capture cross section of 241Am was increased by about 8-9% to reduce the overestimation of criticality observed in the MOX-Fueled light-water-moderated cores using 241Am-rich plutonium-fuel.The revised data gives the better results of criticality prediction for those cores than that with JENDL-3.3. The Pu ageing problem was also investigated using the revised data. This problem is that the calculated k-effs for critical MOX cores with different experiment dates showed the tendency of increase with time. The change of k-eff in seven years was about 0.2%dk/k with JENDL-3.3 and it was reduced to about 0.1%dk/k with JENDL-4.0. These results show that the revision of 241Am capture cross section seemed to be successful, although there still remains the tendency of k-eff increase with time. On the other hand, the recent measurement of thermal and resonance capture cross section of 241Am indicates that the data of JENDL-3.3 should be increased by about 18%, that is about 8% greater than that of JENDL-4.0. In the present study, the possibility of further revision of 241Am capture cross section was studied through the integral test for Pu ageing problem by reflecting the recent experimental data. Three criticality data of a light-water moderated MOX core with different experiment date (7 years interval at maximum) have been analyzed with JENDL-3.3 and 4.0 libraries. In addition, the calculations with the number density of 241Am multiplied by 1.18 for JENDL-3.3 and by 1.08 for JENDL-4.0 were also conducted to simulate the increase of 241Am capture cross section suggested by the recent measurement. The results show that the increase tendency of k-eff as a function of time observed in the calculations with JENDL-4.0 is not found in those with modified 241Am number density. This means that the improvement of 241Am capture cross section will be achieved by employing the recent experimental data.